Ethlene propylene rubber foam and image formation equipment

ABSTRACT

An ethylene propylene rubber foam which comprises as the crude rubber, an ethylene propylene rubber having an iodine value of 35 to 45 and a Mooney viscosity ML 1+4  at 100° C. of 20 to 50, and which has less compression set and is suitable as a material for a transfer member, a primary transfer member, a secondary transfer member, a cleaning member for image formation bodies, a bias member, a backup member, etc.; an electroconductive ethylene propylene rubber foam which comprises as the crude rubber, an ethylene propylene rubber having an iodine value of 35 to 45 and a Mooney viscosity ML 1+4  at 100° C. of 20 to 50, and which electrifies an image formation body through direct charge injection by applying voltage, thus enabling to electrify at low voltage, substantially prevent ozone generation, noises and defective image; an electrifying member comprising the above electroconductive rubber foam; electrifying equipment equipped with the above member; and image formation equipment equipped with the above member or the above equipment.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an ethylene propylene rubberfoam which is improved in its compression set. More particularly, thepresent invention pertains to an ethylene propylene rubber foam wellsuited for use as a material which forms a member to be installed inelectrophotographic equipment and electrostatic recording equipment suchas a copying machine, facsimile equipment and a printer; to a membersuch as a transfer member composed of this rubber foam; and imageformation equipment (I) equipped with the above-mentioned member.

[0003] The present invention is of such a system that directly injectselectrical charge by applying voltage so as to electrify an imageformation body. Thus the present invention further relates to anelectrifying member which comprises an electroconductive ethylenepropylene rubber foam and which is capable of suppressing the generationof a defective image; and electrifying equipment and image formationequipment (II) each equipped with the above mentioned electrifyingmember.

[0004] 2. Description of the Related Arts

[0005] In electrostatic recording equipment and electrophotographicsystem such as a copying machine, facsimile equipment and a printer,there have heretofore been employed a variety of members such as atransfer roller, a bias roller, a backup roller, a toner feeding roller,a cleaning roller and a paper feeding roller in addition to anelectrifying roller used for the purpose of electrifying an imageformation member. As the material for forming the above-mentionedmember, an ethylene propylene rubber foam is used in the majority ofcases.

[0006] The major reasons for the frequent use of the ethylene propylenerubber foam are that said rubber foam is stable against ozone, NO_(x),heat and the like, and has favorable durability.

[0007] However, because of its large compression set, the ethylenepropylene rubber foam is involved in such a problem that the rubber foamsometimes causes defective image due to deformation when a membercomposed of an ethylene propylene rubber foam is brought into contactwith an other member for a long period of time.

[0008] Under such circumstances, an attempt is made to improve thecompression set of an ethylene propylene rubber foam through a method inwhich the content of the rubber component is increased by decreasing thecontents of a filler and/or a process oil in a crude rubber composition.An increase in the content of the rubber component, however, bringsabout such problems that molding processability of the rubbercomposition is worsened and at the same time, foaming cells are madecoarse.

[0009] On the one hand, in electrophotographic equipment andelectrostatic recording equipment such as a printer and a copyingmachine, electrifying equipment of corona discharge system hasheretofore been employed as electrifying equipment for electrifying anobject of electrification such as an electrophotographic photoreceptorand electrostatic recording body. However, the aforesaid coronadischarge system unfavorably requires a high voltage in the range of 5to 10 kV, and besides is involved in an environmental problem due to thegeneration of a large amount of ozone in the course of corona discharge.

[0010] In such circumstances, a contact electrification system hasrecently been put into extensive practice wherein an electrifying memberto which voltage is applied is brought into contact with an object ofelectrification such as a photoreceptor so as to electrify the aforesaidobject. The above-mentioned electrification system is advantageous inthat the applied voltage can be lowered and besides, the ozonegeneration can be decreased as compared with the corona dischargesystem. Nevertheless, the conventional contact electrification system,which majorly utilizes atmospheric discharge that is carried out througha slight clearance between an electrifying member and an image formationbody, has not necessarily been satisfactory, since it is incapable ofsufficiently preventing the ozone generation.

[0011] In addition, the application of direct current voltage only bybringing an electrifying member into contact with an object ofelectrification gives rise to the difficulty in uniformly electrifyingthe object of electrification, thereby causing a fear of unevenelectrification. It is a general practice as a countermeasurethereagainst to superimpose alternate current and direct current,whereby serious problem is brought about in that vibration occursbetween the object of electrification and the electrifying member,inevitably causing unfavorable noise.

[0012] Such being the case, the present inventors proposed theelectrification system in which a charge is directly injected from anelectrifying member to an object of electrification without beingaccompanied with atmospheric discharge {refer to Japanese PatentApplication Laid-Open No.210283/1993 (Heisei-5)}. In the above proposedsystem, electrification is carried out by means of direct chargeinjection by bringing an electrifying member into contact with an objectof electrification so as to apply direct current voltage basicallywithout being accompanied by atmospheric discharge through appropriateadjustment between the applied voltage and the electrostatic capacitiesof the electrifying member and the object of electrification. Thus, saidsystem possesses such advantages that the system enables electrificationat a low voltage, since the voltage for the start of discharge neededfor atmospheric discharge is dispensed with, that the system issubstantially free from ozone generation, and that the system issubstantially free from the problem of noise generation caused byapplication of alternate current voltage.

[0013] As mentioned hereinbefore, the direct charge injection system isa favorable system in principle, but is involved in various problems tobe solved in order that it is brought to practical use. That is to say,unless the object of electrification is brought into close contact withthe electrifying member, part of the object of electrification which isnon-electrified tends to remain. When an image is formed in such astate, there are sometimes caused in part such defects as fog, blackpoints, white points, white streaks, black streaks and unevenness. Whenthe pushing pressure is enhanced in order to bring the electrifyingmember into close contact with the object of electrification, part ofthe aforesaid object is scraped off, thereby causing the problem ofdefective image. As a countermeasure thereagainst it is proposed toconstitute the electrifying member of an elastic foam, but as a matterof fact, the above-mentioned defect and trouble are not yet prevented atthe present time.

SUMMARY OF THE INVENTION

[0014] The present invention was made in the light of theabove-mentioned circumstances. Thus a general object thereof is toprovide an ethylene propylene rubber foam which has improved compressionset and stabilized microcells; a member which comprises the aforesaidethylene propylene rubber foam, and which is used for a variety of imageformation equipment; and image formation equipment (I) equipped with theaforesaid member.

[0015] Moreover, the present invention is of such a system thatelectrifies an image formation body through direct injection ofelectrical charge by applying voltage thereto. Thus another objectthereof is to provide an electrifying member which comprises anelectroconductive ethylene propylene rubber foam and which is capable ofsuppressing the generation of a defective image; and electrifyingequipment and image formation equipment (II) each equipped with theabove mentioned electrifying member.

[0016] Other objects of the present invention will be obvious from thetext of this specification hereinafter disclosed.

[0017] In such circumstances, intensive research and investigation werecarried out by the present inventors in order to achieve theabove-mentioned objects. As a result, it has been found that it is madepossible to obtain an ethylene propylene rubber foam which has improvedcompression set and stabilized microcell foam by using as crude rubber,an ethylene propylene rubber having a iodine value in the range of 35 to45 and a Mooney viscosity ML₁₊₄ at 100° C. in the range of 20 to 50. Ithas also been found that a favorable image is obtainable and the objectsof the invention can be achieved by the use of an electrifying memberwhich is composed of an ethylene propylene rubber foam having a iodinevalue and Mooney viscosity ML₁₊₄ at 100° C. each in a specific range, sothat appropriate contact is attained between the electrifying member andan image formation body, and uniform electrification is made possible.The present invention has been accomplished by the foregoing findingsand information.

[0018] That is to say, the present invention provides an ethylenepropylene rubber foam which comprises as the crude rubber, an ethylenepropylene rubber having an iodine value in the range of 35 to 45 and aMooney viscosity ML₁₊₄ at 100° C. in the range of 20 to 50; at least onemember selected from the group consisting a transfer member, a primarytransfer member, a secondary transfer member, a toner feeding member, acleaning member for an image formation body, a bias member, a backupmember, an electrifying member, a developing member and a paper feedingmember each being composed of the above-mentioned ethylene propylenerubber foam; and image formation equipment equipped with at least one ofthe aforesaid members.

[0019] In addition, the present invention provides an electrifyingmember which electrifies an image formation body through direct chargeinjection by bringing said member into contact with the image formationbody, and applying voltage therebetween, and which comprises anelectroconductive ethylene propylene rubber foam, said rubber foamcomprising as the crude rubber, an ethylene propylene rubber having aniodine value in the range of 35 to 45 and a Mooney viscosity ML₁₊₄ at100° C. in the range of 20 to 50; electrifying equipment comprising saidelectrifying member used therefor; and image formation equipmentequipped with said electrifying equipment.

DESCRIPTION OF PREFERRED EMBODIMENT

[0020] In the ethylene propylene rubber foam according to the presentinvention, there is used as a crude rubber, an ethylene propylene rubberhaving an iodine value in the range of 35 to 45 and a Mooney viscosityML₁₊₄ at 100° C. in the range of 20 to 50. Preferably, theabove-mentioned rubber has an iodine value in the range of 35 to 40 anda Mooney viscosity ML₁₊₄ at 100° C. in the range of 30 to 45. The iodinevalue, when being less than 35, leads to unfavorably high compressionset of 20 to 40% , whereas the iodine value, when being more than 45,unfavorably gives rise to deteriorated resist the ethylene propylenerubber foam against ozone and the like. The Mooney viscosity ML₁₊₄ at100° C., when being less than 20, brings about such disadvantage thatthe viscosity of an unvulcanized rubber composition becomes unreasonablylow, thus causing excessive foaming, whereby the resultant cells aremade coarse, whereas the Mooney viscosity ML₁₊₄ at 100° C., when beingmore than 50, brings about such disadvantage that the viscosity of anunvulcanized rubber composition becomes unreasonably high, thus causinginsufficient foaming, whereby the density of the resultant foam is madetoo high.

[0021] The ethylene propylene rubber foam according to the presentinvention may be blended with other components that are to be optionallyand properly selected, provided that use is made of the above-mentionedethylene propylene rubber. Preferably, the aforesaid crude rubber in anamount of 100 parts by weight is blended with 0.5 to 5 parts by weightof (A) a vulcanizing agent, 1 to 15 parts by weight of (B) a foamingagent, 10 to 80 parts by weight of (C) a process oil and 10 to 60 partsby weight of (D) a filler. The objective rubber foam is obtainable byvulcanizing and foaming the blend thus formed. In the case where theethylene propylene rubber foam according to the present invention ismade electroconductive, 1 to 80 parts by weight of an electroconductivematerial (E) may be blended, followed by vulcanizing and foaming.

[0022] The vulcanizing agent to be used as the component (A) may beselected for use from a variety of vulcanizing agents, but is preferablyof sulfur base from the viewpoint of its capability of facilitatingfoaming and vulcanization of the ethylene propylene rubber composition.By the term“sulfur base vulcanizing agent” as used herein is meant thecombination of sulfur and a vulcanization accelerator, or asulfur-containing organic compound. Examples of vulcanizationaccelerator include thiazoles, sulfenamides, thiourea, thiuram,dithiocarbamates, guanidines, aldehyde amines and aldehyde ammonia. Anyof the exemplified vulcanization accelerator may be used alone or in theform of mixture with at least one other. Examples of sulfur-containingorganic compound include morpholine disulide, tetraalkylthiuramdisulfide and dipentamethylene thiuram tetrasulfide. The amount of thevulcanizing agent to be added to the rubber is preferably 0.5 to 5 partsby weight based on 100 parts by weight of the ethylene propylene rubber.

[0023] Examples of foaming agents as the component (B) include organicfoaming agents such as sulfonylhydrazides that are exemplified byp,p′-oxybis(benzenesulfonylhydrazide) (OBSH), benzenesulfonylhydrazideand toluenesulfonylhydrazide, azo compounds that are exemplified byazocarbonamide (ADCA) and azobisisobutylonitrile, and nitroso compoundsthat are exemplified by N,N′-dinitrosopentamethylenetetramine,N,N′-dimethyl-N,N′-dinitrosoterephalamide; and inorganic foaming agentssuch as sodium hydrogencarbonate and ammonium hydrogencarbonate.Preferable foaming agents among them are OBSH, ADCA and a combination ofthem. The amount of the foaming agent to be added to the rubber ispreferably 1 to 10 parts by weight, particularly preferably 3 to 8 partsby weight based on 100 parts by weight of the ethylene propylene rubber.It is preferable to minimize the particle diameter of the foaming agentin order to decrease the size of foam cells. The particle diameterthereof is preferably 10 μm or smaller, particularly preferably 5 μm orsmaller.

[0024] Examples of process oils as the component (C) that are usablewith the rubber include paraffin base process oil, naphthene baseprocess oil and aromatic base process oil, Of these, paraffin baseprocess oil is preferable from the viewpoint of its property ofnon-contaminating an other member such as a photosensitive body. Theamount of the process oil to be added to the rubber is preferably 20 to70 parts by weight, particularly preferably 40 to 70 parts by weightbased on 100 parts by weight of the ethylene propylene rubber. An amountof the process oil, when being less than 20 parts by weight, bringsabout unreasonably high viscosity of the resultant rubber compositionthus causing poor processability, and at the same time, unreasonablyhigh density of the foam to be produced due to insufficient foaming. Onthe other hand, an amount of the process oil, when being more than 70parts by weight, brings about the disadvantage of unreasonably lowviscosity of unvulcanized rubber composition thus causing coarse celldue to excessive foaming.

[0025] Examples of fillers as the component (D) that are usable with therubber include calcium carbonate, magnesium carbonate, magnesiumsilicate and clay. Of these, calcium carbonate is preferable from theviewpoint of its property of stabilizing foam cell. The amount of thefiller to be added to the rubber is preferably 10 to 60 parts by weight,particularly preferably 20 to 50 parts by weight based on 100 parts byweight of the ethylene propylene rubber. An amount of the filler, whenbeing less than 10 parts by weight, results in unstabilized andnon-uniform foam cell, whereas an amount of the filler, when being morethan 60 parts by weight, leads to unreasonably large compression set ofthe ethylene propylene rubber foam.

[0026] Examples of the electroconductive material as the component (E)include electroconductive carbon black such as ketchen black andacetylene black; carbon black for rubber such as SAF, ISAF, HAF, FEF,GPF, SRF, FT and MT; carbon black for ink such as oxide carbon black,thermally cracked carbon black, graphite; electroconductive metal oxidesuch as tin oxide, titanium oxide and zinc oxide; metals such as nickeland copper; and electroconductive whisker such as electroconductivepotassium titanate whisker, electroconductive barium titanate whisker,electroconductive titanium oxide whisker and electroconductive zincoxide whisker. The amount of the electroconductive material to be addedto the rubber is preferably 1 to 80 parts by weight, particularlypreferably 5 to 60 parts by weight based on 100 parts by weight of theethylene propylene rubber. By adding the above-mentionedelectroconductive material to the rubber, it is made possible to adjustthe specific volume resistance of the ethylene propylene rubber foamaccording to the present invention to the range of 10⁴ to 10¹⁰Ω·cm.

[0027] To the ethylene propylene rubber foam according to the presentinvention, a rubber additive may be properly added which is exemplifiedby a vulcanization accelerator aid such as zinc white and stearic acid,an anti-scorching agent, a tackifier and miscellaneous rubber additivesto the extent that the working effect of the present invention is notimpaired by such addition.

[0028] In the following, some description will be given of a process forproducing the ethylene propylene rubber foam according to the presentinvention, for instance, in the case of producing a roller-shapedmember.

[0029] In the first place, the ethylene propylene rubber is blended andkneaded with the rubber additives other than a vulcanizing agent and afoaming agent at a temperature in the range of 110 to 180° C.,approximately by the use of a kneader, a Banbury mixer or the like. Theresultant kneaded mixture is allowed to cool and thereafter, avulcanizing agent and a foaming agent are added to the mixture andkneaded at a temperature in the range of 50 to 90° C., approximately toproduce a rubber composition.

[0030] Subsequently, by the use of an extruder the resultant rubbercomposition is extruded in the form of cylinder, and cut into aprescribed length. A dummy shaft is inserted into the cylindrical rubbercomposition, which is then set in a preheated mold and is heated at aprescribed temperature for a prescribed period of time (usually at 140to 180° C. for 5 to 30 minutes, approximately) . In order to obtain afoam having uniform and fine foam cells, importance should be attachedto the pressure applied to the mold, which is preferably 9.8×10⁵ to9.8×10⁶ Pa (10 to 100 kg/cm², approximately), particularly preferably1.9×10⁶ to 7.9×10⁶ Pa (20 to 80 kg/cm², approximately). As heatingmethod for the purpose of obtaining the foam, there are available highfrequency heating method, hot blast heating method, fluidized bedheating method, vulcanizing kettle heating method and the like heatingmethod in addition to the above-described mold heating method. Of these,mold heating method is particularly preferable from the standpoint ofits capability of producing an ethylene propylene rubber foam which hasuniform and fine foam cells and also has small compression set.

[0031] After the cylindrical rubber composition is heated at aprescribed temperature for a prescribed period of time, the mold isopened to obtain an ethylene propylene rubber foam. The dummy shaft isremoved, and thereafter a genuine shaft which has been coated in advancewith an adhesive is inserted thereinto in place of the dummy shaft thusremoved, and is heated with hot blast or the like so as to carry outadhesion treatment between the ethylene propylene rubber foam and theshaft thus inserted simultaneously with post vulcanization of theresultant foam. The post vulcanization is put into practice at atemperature in the range of 140 to 200° C. for 15 to 60 minutes,approximately.

[0032] The shafted rubber foam thus obtained is adjusted to a desiredoutside diameter by subjecting the peripheral surface thereof togrinding with a grindstone, peeling with a blade or the like treatmentso as to obtain the objective roller. It is preferable to further carryout an annealing treatment to remove internal stress remaining in theroller, since the compression set is lessened. The annealing treatmentis put into practice at a temperature in the range of 70 to 200° C. for15 to 300 minutes, approximately.

[0033] In addition to the above-mentioned production method, the memberwhich is in the form of a roller and is composed of the ethylenepropylene rubber foam can be produced by a method in which the rubbercomposition is injected into a mold wherein a dummy shaft is set inadvance by the use of an injection molding machine in place of anextruder, followed by heating foaming.

[0034] Such being the case, it is made possible to suppress thecompression set of the resultant foam to 15% or less, and at the sametime to obtain ethylene propylene rubber foam which has uniformmicrocells, a foam density of 0.1 to 0.5 g/cm³ and the average diameterof a foam cell of 30 to 100 μm by the use of ethylene propylene rubberhaving an iodine value in the range of 35 to 45 and a Mooney viscosityML₁₊₄ at 100° C. in the range of 20 to 50.

[0035] The ethylene propylene rubber foam according to the presentinvention is well suited for use as a material which constitutes atransfer member, a primary transfer member, a secondary transfer member,a toner feeding member, a cleaning member for image formation bodies, abias member, a backup member, an electrifying member, a developingmember, a paper feeding member and the like. The rubber foam can be madeinto the form of a roll, blade or the like. In the case of the imageformation equipment (I), one or at least two of these members can befitted thereto.

[0036] On the one hand, the electrifying member according to the presentinvention comprises the electroconductive ethylene propylene rubberfoam. In the aforesaid electroconductive ethylene propylene rubber foam,other components to be blended therewith may be properly and optionallyselected provided that use is made of the foregoing ethylene propylenerubber. Preferably, the above-mentioned electroconductive ethylenepropylene rubber foam can be produced by a method in which the cruderubber in an amount of 100 parts by weight is blended with 0.5 to 5parts by weight of a (A) vulcanizing agent, 1 to 15 parts by weight of a(B) foaming agent, 10 to 80 parts by weight of a (C) process oil, 10 to60 parts by weight of a (D) filler and 1 to 80 parts by weight of anelectroconductive material (E). The objective rubber foam is obtainableby vulcanizing and foaming the blend thus formed. The components (A),(B), (C), (D), and (E) are each the same as those hereinbeforedescribed.

[0037] It is made possible to adjust the specific volume resistance ofthe electrifying member according to the present invention to the rangeof 10⁴ to 10¹⁰Ω·cm. In order to obtain a favorable image, the specificvolume resistance thereof is particularly preferably in the range of 10⁵to 10⁸Ω·cm. The electrifying member according to the present inventioncan be produced by the method same as that hereinbefore described.

[0038] Moreover, the electrifying equipment according to the presentinvention is constituted of the above-mentioned electrifying member anda electric power source. The image formation equipment (II) comprisesthe electrifying equipment installed therein, and may be equipped withone or at least two members that are exemplified in the case of theimage formation equipment (I).

[0039] In the following, the present invention will be described in moredetail with reference to comparative examples and working examples,which however shall never limit the present invention thereto.

[0040] In addition, measurements were made of the physical properties ofthe electroconductive roller obtained in each of the examples inaccordance with the following procedures.

[0041] (1) Physical Properties of Rubber Foam

[0042] (a) Diameter and number of cells

[0043] The diameter and the number of cells of the image were measuredby photography at a magnification of about 70 using a CCD cameramanufactured by Hilock Co., Ltd.

[0044] (b) Asker C hardness

[0045] Asker C hardness was measured according to JIS K6301.

[0046] (c) Density

[0047] Density was obtained by dividing the weight of rubber foam in theair by the volume thereof.

[0048] (d) Compression set

[0049] Compression set was measured according to JIS K6382 (foam rubberfor cushion).

[0050] (e) Specific volume resistance

[0051] Specific volume resistance ρ was calculated from the followingformula using the resistance of the electroconductive roller asexpressed below

R=(ρr ₂ /Ld)ln(r ₂ /r ₁)

[0052] where,

[0053] R: resistance of the electroconductive roller

[0054] ρ: specific volume resistance of rubber foam

[0055] L: contact length in axial direction

[0056] d: nip width

[0057] r₁: shaft radius

[0058] r₂: outside radius of electroconductive roller

[0059] ln: natural logarithm

[0060] (2) Resistance of Electroconductive Roller

[0061] The resistance of the electroconductive roller was measured byapplying a load of 500 g onto each of the ends of an electroconductiveroller as a specimen so that it was pressed to a copper plate, whileapplying 100V voltage thereto and using a specific resistance meter R8340A manufactured by Advantest Corporation.

EXAMPLE 1

[0062] Ethylene propylene rubber (EPDM) having an iodine value of 36 anda Mooney viscosity ML₁₊₄ at 100° C. of 39 in an amount of 100 parts byweight was blended with blending components the types and amounts ofwhich are given in Table 1 by the use of a kneader, so that unvulcanizedrubber foam composition was prepared. By using an extruder, thecomposition thus prepared was molded into a tubular body having aninside diameter of 4 mm, an outside diameter of 20 mm and a length of240 mm. Then the tubular body, into which a stainless steel-made dummyshaft having a diameter of 4 mm and a length of 300 mm was inserted, wassubjected to vulcanization and foaming at 170° C. for 15 minutes in acylindrical mold. The tubular foam thus obtained was placed in an airoven, and further vulcanized at 180° C. for one hour.

[0063] The dummy shaft was removed from the vulcanized tubular foam.Subsequently the tubular foam, into which a metallic shaft with anoutside diameter of 6 mm wound with a hot melt adhesive was inserted bypressing, was subjected to a thermal adhesion treatment at 120° C. for70 minutes, allowed to cool, and polished on the surface, so that anelectroconductive roller having an outside diameter of 12 mm and alength of 220 mm was obtained. The physical properties of the resultantelectroconductive roller are given in Table 1.

Comparative Example 1

[0064] The procedure in Example 1 was repeated to prepare anelectroconductive roller having an outside diameter of 12 mm and alength of 220 mm except that use was made of EPDM having an iodine valueof 26 instead of 36 and a Mooney viscosity ML₁₊₄ at 100° C. of 45instead of 39. The physical properties of the electroconductive rollerthus obtained are also given in Table 1.

Comparative Example 2

[0065] The procedure in Example 1 was repeated to prepare anelectroconductive roller having an outside diameter of 12 mm and alength of 220 mm except that use was made of EPDM having an iodine valueof 26 instead of 36 and a Mooney viscosity ML₁₊₄ at 100° C. of 100instead of 39. The physical properties of the electroconductive rollerthus obtained are also given in Table 1. TABLE 1 Comparative ComparativeExample 1 Example 1 Example 2 COMPOSITION OF FOAM-CONSTITUTING MATERIAL(PARTS BY WEIGHT) EPDM 1⁽¹⁾ 100 — — EPDM 2⁽²⁾ — 100 — EPDM 3⁽³⁾ — — 100Carbon black⁽⁴⁾ 56 56 56 Calcium carbonate⁽⁵⁾ 30 30 30 Process oil⁽⁶⁾ 6060 60 Zinc white 3 3 3 Stearic acid 2 2 2 Vulcanization 1 1 1accelerator⁽⁷⁾ Sulfur 1.5 1.5 1.5 Foaming agent OBSH⁽⁸⁾ 6 6 6 PHYSICALPROPERTIES Electroconductive foam Average cell diameter 30 120 30 (μm)Average number of cells 900 200 900 (per 25 mm) Asker C hardness (°) 3533 45 Density (g/cm³) 0.31 0.28 0.41 Compression set (%) 6 18 16Specific volume resistance (Ω · cm) 3 × 10⁵ 5 × 10⁵ 8 × 10⁶ Rollerresistance (Ω) 3 × 10⁴ 2 × 10⁴ 2 × 10⁶

[0066] {Remarks}

[0067] (1) EPDM having an iodine value of 36 and a Mooney viscosityML₁₊₄ at 100° C. of 39

[0068] (2) EPDM having an iodine value of 26 and a Mooney viscosityML₁₊₄ at 100° C. of 45

[0069] (3) EPDM having an iodine value of 26 and a Mooney viscosityML₁₊₄ at 100° C. of 100

[0070] (4) Manufactured by Tokai Carbon Co., Ltd. under the trade name“TB#5500”

[0071] (5) Manufactured by Nitto Funka Kogyo Co., Ltd. under the tradename“Novelite A”

[0072] (6) Manufactured by Idemitsu Kosan Co., Ltd. under the tradename“Diana Process Oil PW 900”

[0073] (7) 2-mercaptobenzothiazole

[0074] (8) Manufactured by Eiwa Chemical Industries Co., Ltd. under thetrade name“Neoselbon N#5000” {p,p′-oxybis(benzene-sulfonylhydrazide)}

What is claimed is:
 1. An ethylene propylene rubber foam which comprisesas the crude rubber, an ethylene propylene rubber having an iodine valuein the range of 35 to 45 and a Mooney viscosity ML₁₊₄ at 100° C. in therange of 20 to
 50. 2. The ethylene propylene rubber foam according toclaim 1, wherein said rubber foam has a compression set of at most 15%.3. The ethylene propylene rubber foam according to claim 1, wherein saidrubber foam has a density in the range of 0.1 to 0.5 g/cm³.
 4. Theethylene propylene rubber foam according to claim 1, wherein said rubberfoam has foam cells having an average diameter in the range of 30 to 100μm.
 5. The ethylene propylene rubber foam according to claim 1, whereinsaid rubber foam is composed of a rubber composition which comprises 100parts by weight of the ethylene propylene rubber as set forth in claim1, 0.5 to 5 parts by weight of a (A) vulcanizing agent, 1 to 15 parts byweight of a (B) foaming agent, 10 to 80 parts by weight of a (C) processoil and 10 to 60 parts by weight of a (D) filer.
 6. The ethylenepropylene rubber foam according to claim 5, wherein said foaming agenthas a particle diameter of at most 10 μm.
 7. The ethylene propylenerubber foam according to claim 5, which further comprises 1 to 80 partsby weight of a (E) electroconductive material.
 8. The ethylene propylenerubber foam according to claim 7, wherein said rubber foam has specificvolume resistance in the range of 10⁴ to 10¹⁰Ω·cm
 9. A member which isselected from the group consisting of a transfer member, a primarytransfer member, a secondary transfer member, a toner feeding member, acleaning member for image formation bodies, a bias member, a backupmember, an electrifying member, a developing member and a paper feedingmember, and which comprises the ethylene propylene rubber foam set forthin claim
 1. 10. An image formation equipment which is equipped with oneor at least two of the members as set forth in claim
 9. 11. Anelectrifying member which electrifies an image formation body throughdirect charge injection by bringing said member into contact with saidbody, and applying voltage therebetween, and which comprises anelectroconductive ethylene propylene rubber foam, said rubber foamcomprising as the crude rubber, an ethylene propylene rubber having aniodine value in the range of 35 to 45 and a Mooney viscosity ML₁₊₄ at100° C. in the range of 20 to
 50. 12. The electrifying member accordingto claim 11, wherein the electroconductive ethylene propylene rubberfoam has a compression set of at most 15%.
 13. The electrifying memberaccording to claim 11, wherein the electroconductive ethylene propylenerubber foam has a density in the range of 0.1 to 0.5 g/cm³.
 14. Theelectrifying member according to claim 11, wherein the electroconductiveethylene propylene rubber foam has foam cells having an average diameterin the range of 30 to 100 μm.
 15. The electrifying member according toclaim 11, wherein the electroconductive ethylene propylene rubber foamis composed of a rubber composition which comprises 100 parts by weightof the ethylene propylene rubber as set forth in claim 11, 0.5 to 5parts by weight of a (A) vulcanizing agent, 1 to 15 parts by weight of a(B) foaming agent, 10 to 80 parts by weight of a (C) process oil, 10 to60 parts by weight of a (D) filer and 1 to 80 parts by weight of a (E)electroconductive material.
 16. The electrifying member according toclaim 15, wherein the foaming agent has a particle diameter of at most10 μm.
 17. The electrifying member according to claim 15, wherein theelectroconductive ethylene propylene rubber foam has specific volumeresistance in the range of 10⁴ to 10¹⁰Ω·cm
 18. Electrifying equipmentequipped with the electrifying member as set forth in claim 11 whichelectrifies an image formation body through direct charge injection bybringing said member into contact with said body, and applying voltagetherebetween.
 19. Image formation equipment which is equipped with theelectrifying equipment as set forth in claim 18.